Just a couple of points...
None of those looking to escape the Theocracy of Asut know how to operate the Royal Roads.
There is a group of Dwarves within the Mablung society that know how to operate them, but not all Mablung have this knowledge. Those who did have this knowledge were bounced back to their starting point, so only those Mablung who do not have the knowledge to operate the portals were actually able to make it all the way through.
Yes, the few Cyrads on Mithra did indeed set them up, just as they setup the others as well. They did not start or influence the war with the Theocracy, but they did use it to their advantage to do subtle manipulations here and there, to get humans, gryx, sithi, and dwarves to Belynar.
The Cyrads want to repair the damage done (they cannot return home until it is repaired), but they also don't want to reveal themselves either. So they have worked to gather the people and things required to allow the Devastation to be repaired, without creating the conditions for another Devastation.